WINSTON-SALEM (AP) _ BB&T Financial Corp. and Southern National Corp. said Monday that they have agreed to merge so they can compete more effectively with larger banks in the Southeast.

BB&T stockholders will receive 1.45 shares shares of common stock in the new company for each BB&T share. Southern National stockholders will get one share in the new company for each of their shares.

The stock exchange is valued at $2.2 billion, the banks said.

The combined bank will have $18.8 billion in assets and $14.3 billion in deposits. In terms of deposits, it will be North Carolina's largest bank and the third largest bank in South Carolina, the two companies said.

Bank executives said the merger was partly a response to proposed changes in federal laws that will allow banks to establish branches across state lines. The changes, expected to be approved by Congress soon, will make it easier for larger banks from other states to move into North and South Carolina.

BB&T and Southern National can compete more strongly together than the two banks could own their own, the bankers said.

The banks will close about 70 of their 535 offices.

Ten percent of the combined bank's 8,700 employees will lose their jobs. Five percent, or 435, will be laid off, and another 435 positions will be eliminated through attrition.

The banks said 100 positions will be cut at BB&T's headquarters in Wilson, N.C., and 100 BB&T managers will move to Winston-Salem. The rest of the job cuts will be in Winston-Salem.

Savings from the branch closings, layoffs and other cost-cutting measures will total $50 million a year, the banks said.

The merger is expected to be completed by June 1995.

BB&T's shares were up 50 cents to $31.50 in late morning trading on the New York Stock Exchange. Southern Nationals shares were up 62 1/2 cents to $21.75 on the Nasdaq Stock Market.